Present day automobile power steering systems use power steering hoses that are constructed and/or provided with acoustic chambers and the like so as to, in varying degrees, dampen noise generated by the power steering pump and/or steering gear. The prior art is replete with a relatively long history of disclosures that describe devices incorporated inside the power steering hose or connected in line with the power steering hoses to dampen this noise. See for example U.S. Pat. Nos. 5,521,340 and 5,172,729 and earlier patents cited as references therein. However, as to improvements in the construction of the power steering hose itself, the emphasis has been in the direction of developing improved heat resistance, which in turn should result in longer service life in the adverse automotive engine compartment environment. To achieve this, higher temperature materials such as chlorosulfonated polyethylene and hydrogenated nitrile have been used.
The power steering hose constructions usually consist of an annular laminate made up of a multiplicity of concentric tubular members, such as an innermost tube, a tubular reinforcement layer, a tubular friction layer, a second tubular reinforcement layer and a tubular outside cover layer. In some instances, the innermost tube of the hose itself is made up of two separate layers. These layers may be coextruded to provide a high temperature innermost material that would come in contact with the power steering fluid, backed up by a lower cost surrounding material to provide the necessary tube strength. See in this regard the U.S. Pat. No. 5,316,046, issued May 31, 1994. See also U.S. Pat. No. 4,998,565 and the prior art cited in the aforementioned '046 patent.